More precisely, the invention relates to a power supply device connectable to an electrical power supply port of an installation, which moreover comprises at least one electrical system connected to the power supply port.
For example, it may apply to the power supply of an installation of computing center type including an information processing system, comprising at least one computer, needing to be supplied with direct current at extra-low voltage.
By “extra-low voltage” is understood a voltage generally considered as “safety voltage”, which allows an operator to handle without danger any electrical component at said voltage. Such a voltage is moreover generally adapted to the electronic components of an information processing system. Several domains are legally defined in France and in Europe (ELV, SELV, PELV, FELV) but all place extra-low voltages below the threshold of 120 V with direct current and below the threshold of 50 V with alternating current.
The voltage of an alternating current distributed by an electricity distribution network is in general of the order of 220/230 V, which thus represents a priori danger for an operator. On the other hand, it is generally considered that a voltage of 50 V or less does not represent danger to handling. Thus, in telecommunications applications, the transmission data processing systems are generally subjected to a voltage of around 48 V. In aviation, the on-board components are generally subjected to a direct voltage of around 28 V. Finally, a computer type information processing system is generally subjected to a direct voltage of around 12 V.
An information processing system is for example a series of computer servers interconnected in a local network, thus forming a high performance computer, generally described as a HPC (High Performance Computing) computer. In this case, as in other sensitive applications (computer server, desktop or laptop micro-computer, telecommunications radiofrequency station, etc.), it is important that the operation of the electrical system is not disrupted by failures in the current power supply, particularly by micro-power cuts in the alternating current power supply network. Indeed, such failures, even when they only last several hundred milliseconds, can bring about computing errors, data losses or very penalizing malfunctions of the HPC computer.
By way of example, the micro-power cuts are quite frequent, since the administrator of the alternating current power supply network may, as the need arises, have to black out parts of the network. These have in general a duration equivalent to several periods of the alternating current: for alternating current of 50 Hertz, a micro-power cut from ten to twelve periods thus lasts between 200 and 250 milliseconds. Moreover, the restart up a device for converting an alternating current into direct current following a micro-power cut can itself also take 100 to 200 milliseconds, which gives a micro-power cut, seen from the electrical system consuming direct current, which can last up to 450 milliseconds.
Installations comprising an electrical system, for example an information processing system, of the type sensitive to micro-power cuts in the network, generally supply an uninterruptible power supply device, which makes it possible to supply a stable electrical supply and devoid of micro-power cuts, whatever happens in the alternating current power supply network. This uninterruptible power supply is generally connected directly to the alternating current power supply network and comprises as a result a rectifier for conversion of the alternating current into direct current (AC/DC converter function). It is moreover provided with an energy storage device, such as a battery of accumulators or a series of supercapacitors, and an inverter to convert the direct current generated by the energy storage device into an alternating current (DC/AC converter function). Inserted between the alternating current power supply network and an electrical power supply port of the installation, it then stands in for the power supply network to supply electrical energy to the electrical system during micro-power cuts or more serious failures of the network.
Such an uninterruptible power supply device is for example described in the article of Sukumara et al., entitled “Fuel cell based uninterrupted power sources”, published in the 1997 International Conference on Power Electronics and Drive Systems Proceedings, vol. 2, pages 728-733, 26-29 May 1997. This device is placed in a cut-through configuration between the alternating current power supply network and the power supply port of the installation.
Thus, when this device is used for the direct current power supply at extra-low voltage of information processing systems of an installation, the alternating current supplied by the power supply network flows through the uninterruptible power supply device before supplying the installation. Consequently, it is firstly rectified for charging, if appropriate, accumulation batteries of the uninterruptible power supply device then inverted at the output of the uninterruptible power supply device. Finally, it is rectified again inside the installation. Knowing that each AC/DC or DC/AC conversion has in general an efficiency of 95%, such a cascade arrangement of converters has an efficiency of around 85%.
A known solution for reducing this degradation of the efficiency consists in replacing the aforementioned uninterruptible power supply device with double conversion by an uninterruptible power supply device with simple AC/DC conversion. The installation is then directly supplied with direct current and a double DC/AC then AC/DC conversion is thereby avoided. It can then be hoped to improve the efficiency by around 10%.
However this solution is not totally satisfactory because any installation needing to provide at least one circuit breaker, upstream of its power supply port and/or its electrical systems, it is then necessary to provide circuit breakers operating with direct current. At the interruption of current brought about by a circuit breaker in the event of a problem, an arc is created. With direct current, it is much more difficult to make this arc disappear than with alternating current: at 50 Hz, an arc disappears at the worst after 20 ms, whereas the same electric arc has no reason to disappear with direct current as long as the circuit breaker has not burned. Consequently, it is necessary to provide specific circuit breakers of more complex technology, which are then more bulky, more expensive and difficult to find commercially.